1. Field of the Invention
The present invention relates to a method for producing and managing fines and more specifically to a method for pressure spraying and burning a coal dust-water mixture. The invention also relates to a method and system for co-firing a unique coal water slurry (CWS) with conventional pulverized coal (PC) utilizing a unique application of conventional, commercially available equipment.
2. Description of the Prior Art
Costly interruptions to flow and serious environmental dust related problems often occur when handling raw coal at mines, processing plants, power plants and other utilization facilities. The flow of pulverized coal in water is frequently interrupted by blockages caused by unevenly distributed and widely varying wet fines content. Even with well designed materials handling systems, such blockages continue to occur in storage and transport facilities such as bins, railroad cars, silos, chutes, stockpiles, pipes, conveyors, feeders, and air ducts, for example. Well designed systems fail because they completely overlook the detrimental role played by the unfavorable physical properties of bulk coal. Moreover, dust problems are frequently caused when some fine sizes located at or near the surface of the bulk coal become dry and entrain in the atmosphere during transport and handling.
It is important, therefore, that wet fine coal be carefully managed to prevent both blockages and dust losses. Blockages can be prevented by initially separating fines from coarse coal during wet processing at mine sites, and transportating the fines in slurry pipelines to the point of utilization separately from the conventionally transported bulk coarse coal. Dust losses to the environment can be prevented by burning the slurry; or, at some point ahead of the boiler, injecting or packaging the slurry well within the coarse coal. Packaging will prevent the fines in the slurry from locating near the surface and drying and dusting off into the atmosphere. These methods also differ from prior art since they permit the elimination of costly fine coal dewatering and drying at the mine site. Burning of the pulverized coal and slurry in the novel process reduces the cost of energy from coal pulverization at the power plant. The energy cost is greatly reduced because of the use of the previously removed fines as fuel.
To eliminate both blockages and dust losses, problem causing fines are initially removed from coal and later systematically remixed as a slurry to control the coal fines content and bulk physical properties. Fines removal takes place at the mine site during wet processing where the fines are pumped in slurry and later recombined with the conventionally transported coarser pulverized coal. The novel recombination takes place within the furnace. The coal water slurry is cofired and used as a fuel in large steam generators.